For example, Shenhua Ningxia Coal Industry Group Company in Northwest China consumes about 37 million tons of coal annually, and has by-product gasification slag and ash residue of about 4.8 million tons (dry slag). However, a large amount of stockpiled gasification slag has to be buried and disposed by paying high expense resulting from the underdeveloped economy and the small scale of infrastructure in Ningxia Hui Autonomous Region, the used amount of building materials in the region is small, long-distance transportation is not cost-effective. On the one hand, the environmental protection benefits are poor, the coal group is required to pay a huge landfill fee of about 230 million yuan, it imposes a heavy burden on the enterprise; on the other hand, the rain leaching and filtrating (leaching, dissolving and infiltration) results in that the harmful elements in the slag are dissolved, when the harmful elements are infiltrate into the soil and absorbed by plants, it may contaminate surface water and underground water, thereby threat human health. Therefore, it is urgent to carry out research on the comprehensive utilization technology of gasification slag and ash residue, solve the difficult problem of large-scale resource utilization of gasification slag and ash residue, it is critical for the Shenhua Ningxia Coal Industry Group Company to gain both the environmental and economic benefits. The comprehensive utilization of gasification ash residue, which makes up a large share of solid wastes, is an important factor in achieving circular economy in the entire coal chemical project.
At present, in addition to the uses of pulverized coal ash in building materials, road construction, dam construction and an engineering backfill, the use of pulverized coal ash in agriculture have also been explored and researched at home and abroad; although the pulverized coal ash has been employed for improving soil during a long history, and a lot of achievements have been made, the use of pulverized coal ash is prone to cause adverse effects with different type and various degree because of the factors such as the imbalanced physical, chemical and biological properties of the pulverized coal ash. There are a large number of saline-alkali lands, desertified lands, and medium and low-yield fields in the Ningxia Hui Autonomous Region and surrounding areas in the northwest China, which requires a vast number of environmentally-friendly soil remediation ameliorant with high quality and low cost.